For developers who maintain, extend or integrate with the plugin. It covers the architecture, the payment and webhook flows, the data the plugin stores, its safety mechanisms (signature checks, locking, idempotency), every hook, and how to develop and test locally.
Architecture
Design principles, files, boot sequence, drivers and API clients.
Settings storage
Where settings live, every key, and the helpers to read them.
Checkout flow
How a cart becomes Paddle lines, and the one-time, subscription, Billing and Classic checkout flows.
Webhooks
The endpoint, signature checks and how each Billing event and Classic alert is handled.
Concurrency and idempotency
Locks, fresh reads, markers, the renewal state machine and the refund ledger.
Refund internals
How refunds travel from EDD to Paddle and from Paddle to EDD.
Subscription internals
The Recurring_Gateway overrides, status mapping, and pause and resume.
Data reference
Order, subscription and customer meta, options and transients.
Hooks reference
Filters and actions the plugin provides, and the EDD hooks it uses.
Endpoints and front end
AJAX and admin endpoints, and the checkout script’s data and behaviour.
Local development and testing
Sandbox, tunnels for webhooks, logging, simulating webhooks and mocking the API.
Coding standards and releases
Coding standards and the release checklist.
Known limitations
What the plugin deliberately does not do, and why.
Licensing and the Lite upgrade
The License class, its constants and statuses, and how Pro takes over from Lite.
For store owners
For setup and day-to-day use, start with Getting started instead.